title: Structural and magnetic phase transitions in NdCoAsO under high pressures.
abstract: We have investigated structural and magnetic phase transitions under high pressures in a quaternary rare-earth transition-metal arsenide oxide NdCoAsO compound that is isostructural to the high temperature superconductor parent phase NdFeAsO. The four-probe electrical resistance measurements carried out in a designer diamond anvil cell show that the ferromagnetic Curie temperature and antiferromagnetic Néel temperature increase with an increase in pressure. High pressure x-ray diffraction studies using a synchrotron source show a structural phase transition from a tetragonal phase to a new crystallographic phase at a pressure of 23 GPa at 300 K. The NdCoAsO sample remained antiferromagnetic and non-superconducting down to 10 K and up to the highest pressure achieved in this experiment, 53 GPa. A P-T phase diagram for NdCoAsO is presented from ambient conditions to P = 53 GPa and T = 10 K.
authors.affiliation: Department of Physics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Walter
authors.initials: W
authors.lastname: Uhoya
authors.forename: Georgiy M
authors.initials: GM
authors.lastname: Tsoi
authors.forename: Yogesh K
authors.initials: YK
authors.lastname: Vohra
authors.forename: Michael A
authors.initials: MA
authors.lastname: McGuire
authors.forename: Athena S
authors.initials: AS
authors.lastname: Sefat
authors.forename: Brian C
authors.initials: BC
authors.lastname: Sales
authors.forename: David
authors.initials: D
authors.lastname: Mandrus
authors.forename: Samuel T
authors.initials: ST
authors.lastname: Weir